A breviary (from Latin brevis, 'short' or 'concise') is a liturgical book of the Latin liturgical rites of the Catholic Church containing the public or canonical prayers, hymns, the Psalms, readings, and notations for everyday use, especially by bishops, priests, and deacons in the Divine Office (i.e., at the canonical hours or Liturgy of the Hours, the Christians' daily prayer). The word can also refer to a collection of Christian orders of prayers and readings, such as contained in Anglican or Lutheran resources. In general, the word breviary may be used to refer to an abridged version of any text or a brief account or summary of some subject, but is primarily used to refer to the Catholic liturgical book.
The volume containing the daily hours of Roman Catholic prayer was published as the Breviarium Romanum (Roman Breviary) until the reforms of Paul VI, when it became known as the Liturgy of the Hours. However, these terms are used interchangeably to refer to the Office in all its forms. This entry deals with the Breviary prior to the changes introduced by Pope Paul VI in 1974.
Read more about Breviary: Origin of Name, Contents of The Roman Breviary, Elements of The Hours, Celebration